Abbreviate day names on main view buttons

As there is now an additional day button we have less space on the
buttons for text. For now we're just abbreviating although later we may
want to have the full strings for high resolution devices.
Enable day 3 button on main page

The day 3 button (Wednesday) was not enabled nor properly hooked up.
This change fixes that.
Display the correct group in EventListActivity

This patch correctly sets the spin box group in the EventListActivity
based on the item used to navigate there. Previously the Events for the
first event group was always shown.